Projecting apparatus.



E. C.' BALLMAN & E. P. EVERS.

PROJECTING APPARATUS.

APPLICATION FILED AUG.6. 1914.

1. 3 SHEETS-SHEET I.

E. C. BALLMAN & E. P. EVEHS.

PROJECTiNG APPARATUS.

APPLICATION FILED AUG.6. I914.

1,275,120. Patented Au 1918.

3 SHEETS-S ET 2.

E. C. BALLMAN & E. P. EVERS.

PR OJEGTING APPARATUS.

APPLICATION FILED AUG.6- I914.

a SHEETSSHEET 3.

I wmf 21212,

I nnwm c. nnnmrm, or xraxwoon, m) nnwann 2. Evans, or ST. LOUIS, urssom.

' ful Improvements in Projecting Apparatus,

- opticon or movin STATES PATENT ornion.

. rnoinc'rmc urnnnrusa citizen of the United States, and residing at 'Kirkwood, in the county of St. Louis and State of Missouri, .and EDWARD P.

Evans, a citizen of the United States, and

residing at St. Louis, in the State of Missouri, have invented certain new and useof which the following is a specification.

This invention relates to projecting apparatus.

. .The ordinary optical lantern used in stere picture machines comprises a source of light, a condenser adapted to concentrate the light on the slide or film, and a-projecting lens adapted to project an image of the ob ecton the slide or film ona screen. The source of light is necessarily positioned s'ome'distance from the condenser, and the condenser, therefore, receives only the light represented by the solid angle having the source of light as the apex. This ,solid angle forms only 'a smallpart of the total angle, and as a result, therefore, in the ordinary projecting ap aratus only about 311- per cent. of the total ight of the source is collected and projected on the screen. In

view of the fact that only a small percentage of the total light can be utilized the "intensity of this source must be very great, and

it is, therefore, necessary to utilize a high candle power source, such a's-an arc; The are must, however,- be placed ,a considerable distance from the condenser to avoid breakage, thereby causing the solid angle to -be small; in addition,"the high temperature arc isa source of danger, especially in'moving picture machines, where an inflammable lm is used. Apart; from" the low effective efiiciency of this apparatus and the danger involved inits operation, the arc-is. necessarily an unsteady source of light, which re-. quires constant regulation, which regulation can only be accomplished by hand and, therefore. requires,'for its operation, exceptionally skilled operators, and .even then the image will be unsteady.

' Some of the objects of this invention therefore are, to provide a projecting apparatus which will obviate the disadvantages of the present construction, which is characterized by high efiiciency, constancy of operation, which requires practically no attention, and in which the. danger from.

fire is entirely eliminated.

. lnvention,

' Referring to the accompanying Specification of Letters Zl'atent. Patnted Aug. 6, 1918. Application filed August a, 1914. Serlaulo. 855,420.

More specifically stated, the objects ofthis invention are, to rovide a projecting apparatus in which t e source of light is com.-

aratus constructed in accordance W1 p this Fig. 3' is a detail diagrammatical view of the apparatus shown in Fig. 2, showing-the object in another position,

Fig. 41s an. enlarged detail 'diagrammatical view of Fig. 2, showing the distribution of the light on the object,

Fig. 5 is a diagram of a'projecting apparatus, illustrating another embodiment of this invention, and Fig. 6 is a detail, show-.-

ing the object in another position,

Fig. 7 is an enlarged detail diagrammatical view of Fig.5, showinglthe distri bution of light "on the object whenjthis object-is in its two positions,

Fig. 8 is a diagram ofa pro ecting apparatus, illustrating another embodiment of this invention,

Fig. 9 is a diagram of a projecting-afiparatus, illustrating still ment of this invention,

another em Fig. 10 isa diagram of a projecting apparatus, showing another embodiment of this. invention,

'Fig. 11 is a diagram of a projecting apparatus, showing still another embodiment of this invention,

Fig; 12 is a diagram of a projecting apparatus, showing a further embodiment of this invention, and, a a "Fig. 13'is a diagram'of a projecting apparatus, showing a still further embodiment of this invention.

drawings,

and more particularly, to Fig. 10 designates a source oflight, sligh -as an arc, 11 the condenser, 12 the object, and 13 the project? ing lens which projects an imagelof the object on the screen. Upon referring to this figure, it will beseen that the total light received by the condenser 11 is. that represented by the solid angle A having its apex at the source of light, and it will be obvious that this solid angle is only a .small proportion of the total solid angle representing the total light emitted from said source' Referring, now, to Fig. 2, BC represents the axis of the apparatus, 15 the source of light, 16 the object (slide or film), and 17 the projecting lens. A. reflector 18 comprising an ellipiud, formed by revolving an ellipse about is so arranged that one of its foci F is'p'osiinatin tioned at the source of light '15, while its other focus F is positioned 'adjacent' the object 16.' Now, in an ellipsoid,'a ray o'rigat one focus-and incident on the' ellipsoidal surface-will be reflected back to the other focus. when a source of-lightis 'positioned'at one focus of. an elli soidal reflector, the total light will be re acted back and come to a focus at theother focus. If, therefore we utilize an ellipsoidal reflector, placed as shown in Fig. 2, and with the reflecting surface extending behind said source and also beyond the source,-the majorgpart 'of the light from said sourcewillbe concentrated of a complete ellipse is used.

at the other focus. The proportion of the total light emitted,, concentrated at the o'ther focus, increases as the reflecting surface is extended {beyond or front ofthe source of light, but it will he noted that the major part of the emitted. light is thus concentrated .wh'enj one-half and even one'fourth Ifthc object16 is placed in the concentrated beam of li ht, either to the left or to the right of :the ocus F','as shown 'inFigs. 2 and 3-respectively, thisobject will receive the major part of the'light emitted by the source. As a' matter of 'fact, taking both the reflected-and the direct illumination, theproportion of the light emitted. construction, therefore, a source, of light object will receive. practically all of the light from the source. The ima of the object so illuminated is projected y'the projecting lens 17 on the screen.

With this construction, therefore, practically all of the light emitted from the source will be concentrated on the object so that there is no l0ss, and the efliciency will, therefore, be exceedingly high. ,In the practical case illustrated in Fig. 2, the total light concentrated 'on the object will be 8Q percent. and even more, of the total light emitted by the source. It will, therefore, be obvious that, with this construction, the intensity of the source can bevery much. less than the intensity with the prior, construction, as shown in Fig. 1, which. utilized onl 'a small ith this having a candle power of 100 will result in C as the axis of revolution,

It, therefore, follows that,

an image having the same brightness as the image produce by the prior construction,

shown n Fig.1,"when a-source, such as an I are, havin a candle power of 2000 is used.

Althoug the apparatus shown in Figs. 2

and 3 has a high efliciency, the intensity of the light on' the. object illuminated is not uniform, but this intensity decreases from near the center outwardly, thereby forming a bright ring. This is .shown in Fig. 4,

where the curvesa designate the intensity 1 curves, the abscissae representingintensity of;

illumination. It will thus be seen that, theoretically, there will be a comparatively dark spot in thecenter, andthen a bright ring which will shade down in intensity toward the outside circumference, and also toward ;the center. The direct illumination-will, of .course, equalize and flatten out the curve slightly, especially at the center,-as indicated by the dotted line b, but even in this case, the illumination will not be uniform.

In accordance with -.this invention, however,

the reflector is so constructed, or means are .provided'for causing the distribution .of the -light on the object to.be uniform. Such a construction is'shown in Figs, 5- to "12 inelusive.

6 and 7 represents the axis'ofrevolution of the surface of revolution forming the. reflecting surface of [the reflector. In this case, however, the surface -0 f revolution is generated by an ellipse section 20 having its axis displaced with respect to. the axis of Q r 100 revolution. In this particular embodiment,

the axis of the ellipse-sectionisshown at" DE, and this axis isdisplaced at an angle .withrespectto the 'axis and passes through the focus F. The other focus of the ellipse section. 20 is B'-G. Therevolution of the". ellipse section 20'about the axis -B-C'w ill,. therefore,

form a distorted ellipse which, in this case,

I is ielairpanded, and, since the ellipse axis D-E.

nerate a'cone the locus of thefo'cusj will a circle. The lower shown at z, and this 'focus is located above the axis 0 revolution 'sition of the focus is shown at f, and .t of axis DE,

7 "showsthe illumination ,cu'rves below the axis 13-70, or at .1-

formed with this reflectorat the object, when in the two positions shown in F 5 and 6. It will be seen that the parts of t e reflector on diametrically opposite sides will a curves'which are reverseI 7 arranged. At the planeto the left of the oci f, f the curves are separated so as to leave a dark spot at the center, surrounded by a bright ring. To the right, however, the curves come together and overlap. The resultant curve 0, shown in dot and dashlines, is, therefore, substantially uniform throughout. 'In case a contracted ellipse is used, the action is reversed, so that planes to the left of the foci that the source of lightis not a point, even when a filament, and considering also the directiillun ination, whichis greatest at the center of the eboot and diminishes toward the outside it w readily "be'seenthat the resultant illumination curves will be nearly s'funiform throughout.

flab With this construction, therefore, the illumination of ther object is substantially ther'eforq-ih addition to concentrating the major pirtof the light from the source on the object, causes a uniform illuminationof the object so that the projected image will also be uniform.

Fig. 8'shows a construction in which a ect 16. This lens is used partly for the purpose of bending the beams outwardly and focal length reflector to be used, and Eartly engthen" g them, so as to permit a short to disperse the light before it strikes t e objecti so as to renderthe illumination more structions shown in Figs. 5 'and 6, as well as.

uni orni by flattening; out the intensity curves shown in Fig. 4. The construction of the reflector is,in this construction, shown as the same as that shown in Fig. 2, but this negative lens may also be applied to the-conthe constructions hereafter described.

-In Fig. 9, the reflector is a compound construction coniprisi5 an ellipsoidal reflector 25 having focr-F, and a spherical reflector 26-having the focus F as a center. In this-construction, the beams paxin outside of the reflector 25 will strike the re ector 26. I

and will; be reflected back through the center or focus F, the elliptical reflector surface25 and; beingreflected back to the other focus F, as shown in Fig. 9; In orderto utilize asmuch light as possible, seci 'cessi'vely increasingoradii extend beyond the Y Y reflectors. 26 and The actionof these reflectors 27 and 28 is the roduce a.'

This construction,

of the-focus r In ,the constr tioual spherical reflectors 27 and '28 of sucund the beam of light.

tion, therefore, the reflector 25 will, by single reflection, and the reflectors 26, 27 and 28 in combinat on with the reflector 25 mm, by double reflection, cause substantially all'of the light emitted from the source 15 to be concentrated on the ob'ect 16. The reflector 25-mayalso bea sp ericalreflector. In this case, the light-15 is placed between the cen er and the reflector, and preferably close to the reflector, wh i1e the reflectors 26, 27 and 28 have their centers at the source.of light as before. While such a device will cal surface 21,- will, by double reflection, be

concentrated at F',' as in the construction shown in Fig. 9, and as also shown in Fig.

10. This construction possesses the advancause concentration of light on the object, it v 'is not as satisfactory as. the construction shown in Fig. 8.

as e" concentrated at tage in thatit ermit's more space rearwardly I to receive the source of light 15,'a nd 'is especial advantage in small devices.

single focus, and this source oflight may be an incandescent lamp of comparatively low candle power, and having a closely looped- F' 11 and 12 show construc-' filament.

ioo

tions in whiclrth filam nt is a rin and in" f Referring first to'Fig. 11, 35" designates a;

section of an ellipse having an axis H-I V and having .foci F.f. This ellipse, is so positioned that its axis cuts the axis of revolution B-C and so' that one focus F will be positioned above the'axis, whiletheother focus f will be positioned below the'axis. The, surface :of revolution will-,- therefore, be

a com ound ellipsoidwhose foci form' cir cular oci having the axis B'C as centers.

The sourceof light comprises a filament 36,

circular inform and placed in a. ring sha ed bulb 37, andfollowing. the locus of the oci 1F; F whereby each part of the filament will v itioned atlthe focus of the ellipse. I.

Wit this construction, the lightfrom the source will be concentrated on-the object 16,

as in the other constructions. The'int'ensity;

curves will-be very similarto-those'shown in 'Fig. 7, so that the distribution of the light,

onthe'object will be substantially uniform' throughout 'This reflectormay'also beso" ction shown in Fi 2 to 10 f inclusive, the source of light is p aced at a negative or plane-convex lens 21 is interposed between the reflector 18 and the obconstructed that the focus f is above the axis iilamenti'will' be, closely coiled, while in the BC, so that the beams of light will not cross as in Fig. 11.

The object 16 may beplaced either inside of thefoci f, f, or outside of these foci, in-

the manner shown in Fig. 6. -In each-case, the major part of the lightemitted by the source will be concentrated on the object, and the intensity of illumination will be substan-. tially uniform. 'Theprovisionof a circular for high power a paratus. It will be under It will, therefore,

latter cases will bea ring.

The efliciency of the. apparatus will, therefilament following the locus of the fociF, F ermits a high voltage incandescent lamp to. be used, thereby adapting this con'struction fore, be very high, permitting 'lo' w candle power sourcejof -.low candle power source not only lessens the the use of a ight; Such a {danger fromifire, but also protects the'appa suitably supported in the reflector from the rear, and the electrical connections are suitabl madeto a source of electric current.v I

the construction shown in Fig. 12 the surfaceof the reflector is formed by an e] ipse 40 having its axis J K at an 'o t use angle -with res ect to the axis of revo-j .1utionBC so as to orma compound ellipsoid having the cross section shown in the figure. The generating ellipse has foci F, F and these foci, as in the constructionshown in Fig. 11,;are positioned or have their loci in circles. having their centers .on the axis B-f-C. The source oflight, which comprises a filament 36, similar to that shown ingFig. "11', is arranged to lie along the locus of the foci 'F, F. A conical mirror 41 4 is positioned inside fof the reflector so as to receive the'li ht onits reflecting surface:

tfiis mirror surface with respect The angle of to the axis M is such thatthe beams reflected from the mirror surface will come to a focus at f, having a circular locus. The object 16, t erefore, receives the beam of light issuing from the reflector, this beam being concentratedon'the object and illumis hating the same uniformly, as in the other constructions. f'

v Fig. 13 shows a construction in which the. elliptical reflector 45 formsithe bulb forthe'f. source of,light.1In this construction the foci. are shown atjF, F", the source of light (fila-l. ment) being positioned at one focus lfiand. thelight from this source coming to}: focus *ratus. 7 Since this construction permits the use of anincandescent filament'adaptedto (Figs. 11 and 12) this filament 1 operate from a constant voltage system, the intens'i of illumination may be kept constantawithout attention from .the operator.-

This feature, in connection with the uniform distribution of the. light on the object illuminated and to be. rojected, results in an image which is uni orm and constant.

f It is obvious that various changes may be made in details of construction without departing from the spirit of this invention,

audit is, therefore, to be understood that this invention is not to be limited to the specific construction shown and described. Having thus described the invention, what is claimed is:

. ofs sai'dobject on.a screem, g v

V m n g a il-solirce oflight, auellipsoidal reflector mject, and means 1. A pro ectingapparatus comprising an ellipsoidal reflector, a source of light positi'oned at the focus ofsaid reflector so as to cause the latter *toconcentrate the; major part of thelight from said source on an obforfprojectingimage of the object on. a

- 2. A apparatus comprisingfan ellipsoi' a1 reflector, an object positioned adjacent one of the .foci. of 851d j'reflector, fa L 1 source of light, positioned inside; of said -reflector at the other focus-thereof so. as to :cause". said reflector conofitrate the. major part-of the'li'ghtifrom said source: on said,

object, and ,means forprojecting an image 1 -53: A pro fting apparatus .c'losin -said source. of light, said some 'of at F and be ng onthwobject. "16. s The bulb, with theexeeptionof the. sur

fmbounded by the line 4 i pr s n issu n at the 1 mm ef-llight m,-ob ect, is "lvered-i d reflecting fsjurface,-2 but is "left: iinsilvei'd' wherethe of f'construction is of-"adv'an j l l since thebulb there orms'*thedoublefunction .of a bulb and a concentrator."- HY iE K he" reflector 45 .ia-a simple ellipsoid'iformed 1' the construction shown shown in Fi 2. f ThlS bulb may, however, be a compoun ellipsoid of the formshowmin' Figsfi l c iye; Iii-m th light ing positionedat oneof the foci of.

"- said-reflector, an. object positioned adjacent- "the other focus-lofsaid reflector, whereby "said reflector concentrates the lighten said emce -m an f r? projecting s r *of sjaidobject o'n'a projecting a paratus comp1 'isingga source, of light, an" o ect,i'an ellipsoidal-1efietor I constructed mid..- arm a with 're'- spect to-said' source and, said 0 ject to-'con--. Zcentrate the ma jorf of the light on ,thelpobject, and: means. for

projecting: .Of saidon-.a'

6.1-A projecting apparatus comprising a source of light, an object, an ellipsoidal resaid source, and -means for projecting an flector positioned with one focus at said source and with the other focus adjacent lsaid object, said reflector extending behind said source, and means for projecting an image of said object on a screen.

6. A projecting apparatus compr sing a source of light, an object, an ellipsoldal reflector constructed and arran spect to said source and'said objectto rece ve and concentrate. on said object the major part of the rays emitted by said source and means for projecting an image of said onascreen. p I

7. A projecting a paratus comprising. a source of light, an o ject, an ellipsoidal. r e flector positioned with one focus at sa d source and with the other focus 'adi'acent said object, and constructed to rece've and concentrate on said object therays impinging rearwardly from said source, ar d means for projecting an image of sald object on a screen. 8.. A projecting apparatus compr slng a source of'light, an ob ect, an elhpsordal reflector constructed and arranged with respect to said source and said object to concentrate the light from said source umformly on said object, and means for projecting an image of said object on a screen. 9. A projecting a paratus compr sing a source of light, an o ect, an ellipsoidal reflector constructed and arranged wlth respect to said source and said object to -receive and concentrate uniformly on said ob-- .ject the major part of the rays emitted by imageof said object "on a screen.-

40' flector arranged with respect to said source 10. A projecting apparatus comprising a source of light, an object, an elhpsoldal reand said object to concentrate the light on said object, and- 'constructed'to distribute the light uniformly on said object, and means for projecting an image of sald object on a screen.

a 11. A projecting apparatus comprising'a source of light, an object, an ellipsoidal re.-

flector positioned with one focus at said source and with. the other foeus ad aeent saidobject, means for distributmg the l ght from said source uniformlyion said object, and means for projecting an image of and object on a 12. A rojectingapparatus comprlsmg a source 0 light, an 'object an ellipsoidal r eflector positioned with one; focus at said source and with the other focus ad acent said object, said reflector belng said source on said object,'and means for projecting an image ofsaid object on' a d withreobject distorted .to. control the distribution of the light from.

flector having'a plurality of foci at one end and arranged with respect to said source and said object to concentrate the light from said source on said object, and means for projecting an image of said object on a screen. I

14. A projecting apparatus comprising a source of light, an object, an ellipsoidal reflector having a plurality of foci at one end, said source being at one focus and said object being adjacent another focus, and meansfor projecting an image of said object on a 7 screen.

15. A projecting apparatus comprising a source of light, an object, an ellipsoidal reflector having its elliptical axis displaced flector having its elliptical axis displaced angularly with respect to its axis of revolution source on said object, and means for projectlng an image of said object on a screen.

17. A projecting apparatus comprising a flector having its elliptical axis displaced i and arranged with respect to said source and said object to concentrate the light from said .95 source of light, an object, an ellipsoidal re with respect to its axis of revolution to form a plurality of foci at one end, and arranged with respect to said source and said object to concentrate the light from said source on said object, and means for projecting an I image of said object on a screen.

. 18.- A projecting apparatus comprising a source oflight, an object, an ellipsoidal reflector constructed'to form a zone of uniform intensity, said reflector being arranged with. respect to said source and said object to concentrate the light from said source on' said object, and means for projecting an image of said ob ect on'a screen.

119. A projecting apparatus comprising a source of light, an object, an ellipsoidal re flector having said source at one focus and said object adjacent the other focus, said reflector being constructed to form a zone of uniform intensity at said object, and means for'projecting an image of said object on a screen.

20. The combination with a source of -light, of an ellipsoidal reflector having a plurality of foci at one end. v p

21. The combination with a source of light, of an ellipsoidal-reflector having its elliptical axis displaced angularly with respect to its axis of revolution.

23. The. combination with a source of light, of an ellipsoidal reflector having its elliptical axis displaced with respect to its axis of revolution to form a locus of foci at one end. I

24. The combination with a source of light, of an ellipsoidal reflector constructed to form a zone of uniform intensity.'

25., The combination with a source 7 oflight, of an ellipsoidal reflector constructed to form a zone of uniform intensity adjacent one focus when said source is at the other focus.

26. X Projecting a paratus comprising a source 0 light, an o ect, a reflector comprising. a surface of. revolution constructed and arranged with respect to said source and said object to concentrate the major part of the light from saidsource on the ob and means for projecting an image ofsai v object on a screen.

27. A Pro ecting. a paratus comprising a source 0 l1ght,. an o ect, a reflector comprising a surface of revolution constructed:

and arranged with respect to said source and said object to. receive and concentrate on said object the majorpart of the rays emitted by said source, and means for projecting an image of said object on a screen. '8. A protecting apparatus comprising a source of lig t, an ob ect, a reflector comprismg asurface of revolution constructed and arranged with? respect to said source and said object to receive and concentrate uniformly on said. object themajorpart of the rays emitted by said source, and means for pro-' jecting an image of said object on a screen.

FI'OJGCtiIlg agparatus comprising a 29. A source 0 light, an o ject, a reflector, com prising a surface revolution arranged with respect to said source and said object to concentrate the light on saidobject, and con- Y H structed to distribute the light uniformly on said objectgand means for projecting an tures in the presence of these two witnesses; 

